Improved Rectification and Osmotic Power in Polyelectrolyte-Filled Mesopores

Abstract

Ample studies have shown the use of nanofluidics in the ionic diode and osmotic power generation, but similar ionic devices performed with large-sized mesopores are still poorly understood. In this study, we model and realize the mesoscale ionic diode and osmotic power generator, composed of an asymmetric cone-shaped mesopore with its narrow opening filled with a polyelectrolyte (PE) layer with high space charges. We show that, only when the space charge density of a PE layer is sufficiently large (>1×106 C/m3), the considered mesopore system is able to create an asymmetric ionic distributions in the pore and then rectify ionic current. As a result, the output osmotic power performance can be improved when the filled PE carries sufficiently high space charges. For example, the considered PE-filled mesopore system can show an amplification of the osmotic power of up to 35.1-fold, compared to the bare solid-state mesopore. The findings provide necessary information for the development of large-sized ionic diode and osmotic power harvesting device.

Space charge enhanced ion transport in heterogeneous polyelectrolyte/alumina nanochannel membranes for high-performance osmotic energy conversion

“…For fair comparison, all measurements of the output current density and power density were carried out with an effective testing area of $3 Â 10 4 mm 2 , the same as that used in the previously reported studies. 22,23,25 Multiphysics simulation All current-voltage (I-V) curves of the PE/nanochannel system under consideration in the absence and presence of a salinity gradient were simulated by simultaneously solving the modied Poisson-Nernst-Planck and Stokes-Brinkman equations, 62 which have been proven to be accurate in capturing the underlying physics of ion transport property in similar PE-based nanouidic systems. 16,[63][64][65] To receive an affordable computational cost, we simplied the Naon as a PE layer bearing a uniformly distributed space charge density of À5 Â 10 7 C m À3 , in accordance with the typical values of synthetic polyelectrolytes (ca.…”

Enhanced Ionic Current Rectification through Innovative Integration of Polyelectrolyte Bilayers and Charged-Wall Smart Nanochannels

“…As it is shown, the highest rectification factor has been attained for each type of the nanochannel when the surface charge density is σ = +10 mC/m 2 and the exterior surface of the LBL soft layer contains a positive charge. 40 At this surface charge density, the rectification coefficient for nanochannels of type (III) was 30.61. When σ = −10 mC/m 2 , the nanochannel exhibits a distinct behavior because the charge sign of the outer soft layer differs from the charge density sign of the hard surface.…”

Nanofluidic osmotic power generators – advanced nanoporous membranes and nanochannels for blue energy harvesting

“…188,207 On the other hand, the creation of systems with a distribution of net charges within the entire volume of the nanochannel interior (space charge) rather than just on the nanochannel walls (surface charge) has demonstrated to be a simple way to improve the SGE performance. 65,118,208 In the last few years, asymmetric modications producing heterogeneous membranes composed of two different monolayer porous membranes have been used as an essential strategy to boost the power in NRED systems. 209,210 In 2019, Wei Guo and coworkers carried out a PNP-based study on the fundamental aspects of heterogeneous membranes as osmotic nanogenerators.…”

“… 63 It is worth noting that in some systems, the I – V response can be slightly non-linear and the employment of eqn (26) could lead to little deviations in the P max estimation. 118 In these cases, representing power vs. voltage ( P – V ) curves and obtaining P max graphically could be the best option. In the latter method, the extracted osmotic power is transferred to an external circuit with an electronic load ( eqn (24) ) ( Fig.…”